It is possible that some bactrians migrated to form settlements in Punjab region during the time of the Ramayana/ Mahabharata. They assimilated to an extent but did not completely adopt the vedic culture, so though they were political and marital alliances, they retained part of their non vedic culture. They were ridiculed because of that.
They intermarried with the other vedic people since the ancestors of the Kauravas and Pandavas were Bahlikas (Kuru dynasty with origins in Uttarakuru). But the Kauravas and Pandavas did not consider themselves as Bahlikas any more despite the Pandavas mother being a Bahlika princess.
