You do not need to have been an (Asian) Buddhist in a previous life in order to be a (Western) Buddhist now. The accumulation of merit necessary for one to come into contact with Dharma is not the monopoly of Buddhists. If it was then there could not have been any Pratyeka Buddhas or enlightened beings before Buddhism. Consider also the number of "Western" Buddhists that existed in Bactria during the growth phase of Buddhism in India. Were they all reincarnations of dead Indian Buddhists? I don't think so. Were they necessarily students of Kassapa Buddha or any of the other 27 Buddhas of this age? Not necessarily. Merit leads one onto and along the path of Dharma.
Abhisanda Sutta: Rewards
translated from the Pali by Thanissaro Bhikkhu
"Monks, there are these eight rewards of merit, rewards of skillfulness, nourishments of happiness, celestial, resulting in happiness, leading to heaven, leading to what is desirable, pleasurable, & appealing, to welfare & happiness. Which eight?
"There is the case where a disciple of the noble ones has gone to the Buddha for refuge. This is the first reward of merit, reward of skillfulness, nourishment of happiness, celestial, resulting in happiness, leading to heaven, leading to what is desirable, pleasurable, & appealing; to welfare & to happiness.
"Furthermore, the disciple of the noble ones has gone to the Dhamma for refuge. This is the second reward of merit...
"Furthermore, the disciple of the noble ones has gone to the Sangha for refuge. This is the third reward of merit...
"Now, there are these five gifts, five great gifts — original, long-standing, traditional, ancient, unadulterated, unadulterated from the beginning — that are not open to suspicion, will never be open to suspicion, and are unfaulted by knowledgeable contemplatives & brahmans. Which five?
"There is the case where a disciple of the noble ones, abandoning the taking of life, abstains from taking life. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the first gift, the first great gift — original, long-standing, traditional, ancient, unadulterated, unadulterated from the beginning — that is not open to suspicion, will never be open to suspicion, and is unfaulted by knowledgeable contemplatives & brahmans. And this is the fourth reward of merit...
"Furthermore, abandoning taking what is not given (stealing), the disciple of the noble ones abstains from taking what is not given. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the second gift, the second great gift... and this is the fifth reward of merit...
"Furthermore, abandoning illicit sex, the disciple of the noble ones abstains from illicit sex. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the third gift, the third great gift... and this is the sixth reward of merit...
"Furthermore, abandoning lying, the disciple of the noble ones abstains from lying. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the fourth gift, the fourth great gift... and this is the seventh reward of merit...
"Furthermore, abandoning the use of intoxicants, the disciple of the noble ones abstains from taking intoxicants. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the fifth gift, the fifth great gift — original, long-standing, traditional, ancient, unadulterated, unadulterated from the beginning — that is not open to suspicion, will never be open to suspicion, and is unfaulted by knowledgeable contemplatives & brahmans. And this is the eighth reward of merit, reward of skillfulness, nourishment of happiness, celestial, resulting in happiness, leading to heaven, leading to what is desirable, pleasurable, & appealing; to welfare & to happiness.