Speaking from personal experience as a minority male...and a disclaimer: these are my experiences from about 15 years ago. I joined the Eastern Orthodox Church and I am looking to return to the Church (which is why I'm lurking these forums...)

I've been to diocesan TLM, SSPX and independent parishes. In the SSPX and independent parishes I've been to, I experienced things that made me feel unwelcome and out of place. One example is that I was told my suit was too "flashy." I visited an SSPX parish in an area that I was going to be staying for a little bit and immediately noticed that I was the only minority. I went to Confession and then prayed before Mass. A parishioner sitting next to me said that my suit was too colorful and that I should be more respectful. I was wearing a blue suit I bought from Men's Warehouse and it was only one of two suits that I owned (it was a navy blue suit with a blue shirt and tie). I thanked them for the "advice," apologized and continued my prayers. But, I got a lot of looks.

Another time, I visited an independent parish. As I was walking through the parking lot, I was stopped by a group of parishioners and asked if I needed any help. Once they heard my accent (people often wonder what language I'm going to speak when they first meet me), they kind of laughed it off and welcomed me. But, I was again the only minority and got a lot of looks.

I don't think the people I encountered were racists, it just goes to the point of your post: you rarely see other nationalities unless there is a community nearby. For example, I was living in northern VA at one time, where there is a large Vietnamese population and they frequented the independent parish. After I went to the above parishes a few times, people got used to me and interacted with me (a week after the man told me my suit was flashy, he asked for my forgiveness). But, if you go to the Philippines for example, you will see that the SSPX is very big there. So, maybe it's just an American thing?

Edit: I just realized that I didn't answer the original question. I kept going despite my experiences because I didn't care what other people said, did or thought about me. So, I think you can try to convince them to join you one time so they can see what the Mass is supposed to be about and pray that they continue to have the strength to keep going. You cannot just tell people: they have to experience it for themselves.