This is what I'm trying to tell you... its not a religion like that. There are cults (in the neutral, academic sense of the word) and worship groups you can join, and depending on who they are, foreigners will or will not be welcome. Many will actively invite you, as a foreigner in (many are probably hurting for new blood; old people looking for someone to pass this stuff on to). They might even let you become a priest. There are some shrines that it makes absolutely no sense that a foreigner would want to have anything to do with. They might let you get married there and bless your marriage - this is how shrines make money and keep up their ancient buildings. But if you understand who that kami is, and the meaning and significance the kami has, it would be very very strange for a foreigner to patronize that kami.
Like I said, most people don't think that hard about any of this one way or the other. The context of this thread is how it fits in Nichiren buddhism. In this context, all that stuff matters and matters very deeply.
There is a system of imperial and other grand shrines - these are some of the biggest and most famous shrines that have to do with the imperial family, creation myths, and special identity with the Japanese people. These are the shrines that use the term Shinto for what they are. Shinto has also come to refer to the general sensibility, beliefs, and rituals, but this is a relatively modern phenomena. There wasn't a background to distinguish "Shinto". Its just the mountain. Its just the waterfall. Its just the reverence and rites of worship that are carried out to please and supplicate them.
Next time you are out and about, if you come across a big, old, remarkable tree, or a remarkably shaped or positioned boulder, a kami probably resides in it. Go up to the tree or rock with a mind of reverence, bow to the tree twice, clap twice, bow again, and be on your way. You've just practiced "Shinto".