I'll approach , talk to and ask them or whatever. Rarely do I see or encounter American born kids playing pickup soccer. At least not since 1974 since I started playing in the South Bay Area. Again, if it is organized I see tons but never just for fun.
I grew up in a small town in East Tennessee and in the 80's we had a really large youth soccer rec league. When I think back to it now it is pretty amazing in this small redneck area in the 80's we had a soccer league with such high participation. We had a pretty good thing going soccer-wise. My town was also home to a missionary flight school. So we had a large number or college age guys that spoke English (most were American) and grew up in other countries playing soccer. These guys knew the sport well. They made up the majority of the coaches and refs for our league. It was a pretty unique situation where you had this southern town in the 80's with very knowledgeable soccer IQ's coaching and ref'ing. We had pick up games with people from middle-school ages to old guys every Saturday for years and years. The flight school closed down/moved 15 years ago and I am not sure if there are still pickup games and not sure how well the rec league is doing these days (it does still exist). Not sure what if anything my story contributes to the discussion. Just wanted to share.
I grew up in suburban Buffalo in the 1970s. There was a sizeable recreational soccer league, but also my friends and I regularly played shirts-versus-skins pick-up soccer games in the park, with shirts from the skins team marking the goals. We played every day after school and all summer long, mixing up our sports. We even played street hockey in July. Forty years later there's still the white rectangular outline of a soccer goal painted on the red brick outside wall of my elementary school gymnasium where I would practice shooting soccer balls on my own or with my best friend, who was starting goalkeeper for the high school team.