While Kalmyk Buddhism is geographically in Europe, it is in a very peripheral part of the continent with virtually no impact on European culture in general. So, it is still reasonable to claim that Buddhism is something foreign to Europe. After all, Buddhism only began to have a real impact culturally in the 19th century with translated literature coming from India and East Asia, not Kalmykia.
With regard to Islam in geographical Europe, yes there is Tatarstan (and bits of adjacent regions), but Muscovy conquered that Muslim power in the mid 16th century and subsequently made it very clear that while Islam exists there, it is only at the mercy of Christian rulers. Historically, during the tsarist era Muslims were forbidden from trying to convert the Christian population.
Perhaps a better example of "Muslims have been in Europe for a long time" (excepting Ottoman converts, as they are seen as forced conversions/uninvited guests/traitors by nationalist demagogues) would be those Tatars (same name as the Kazan Tatars but not closely related) who settled in the Polish-Lithuanian Commonwealth, but again their impact on the surrounding culture was minuscule, and ultimately they assimilated into the Slavic-speaking Christian population.
With regard to Islam in geographical Europe, yes there is Tatarstan (and bits of adjacent regions), but Muscovy conquered that Muslim power in the mid 16th century and subsequently made it very clear that while Islam exists there, it is only at the mercy of Christian rulers. Historically, during the tsarist era Muslims were forbidden from trying to convert the Christian population.
Perhaps a better example of "Muslims have been in Europe for a long time" (excepting Ottoman converts, as they are seen as forced conversions/uninvited guests/traitors by nationalist demagogues) would be those Tatars (same name as the Kazan Tatars but not closely related) who settled in the Polish-Lithuanian Commonwealth, but again their impact on the surrounding culture was minuscule, and ultimately they assimilated into the Slavic-speaking Christian population.