There is capital gain tax exemption for your primary residence

up to $250,000 for a single person and up to $500,000 for a couple filing

jointly if you lived in that house at least for two years out of past 5

years at the point you sell the house. You get the exemption even if you lived

there less than 2 years if you had to sell the house for imperative reasons such

as your job transfer.

Your realtor’s comment is unheard of. I can’t see why foreigners should be different.

realtors are not nessessarily tax specialists. I think you need to make a call to an accountant.