If thats the only transformation that you have to deal with - thats commercial. Heck living in Europe, I even remember the days where we didnt have a Halloween, before we imported it from the US. For us those were they days where we visited the resting places of our loved ones, not gave out candy and bought plastic skeletons, or wore costumes to parties.
If those are the things you remember fondly - no one actually took them away in a big ruse, its just merchants trying to sell the stuff in the least offensive way possible to as many people as possible.
Also - on the part of the separation of state and church on a very basic level, both are systems that reporduce a certain kind of order. Both clashed in the past, the church didn't win - but was still important enough to be granted huge tax benefits and even the power to take in money through certain state venues. Both systems coexist - and if you look at the benefits of science based temples, in terms of economic growth alone - churches couldnt have even competed - you would have found yourself in one of those second world countries, you are now worried - that would take over your society... :/
And the truth is, especially when we look at the "middle east refugee crisis", the US didn't own up to any responsibility it historically and regionally/politically had. The numbers in the scaremongering Canada video, were laughingly small compared to what Europeans had to deal with, not to even speak of egyptians, turks, or other somewhat stable states in that region.
The US excuse was always "we are afraid of terrorists" - but those people, at large fled because of violent conflict in their regions, that wasn't entirely unrelated to our foreign politics (to put it mildly).
You'll take them in, you deal with it. You close your borders - if your own society rebels against it, because right wing populists make this about "them eating away your tax payers benefits". The truth is, as a large country - you can get money to board them up for a few years, and some of them even for life - for free. Even the relationship you have with those nations, post conflict - when people return (and many of them will) are worth more than feeding and boarding up those people for five or six years. In monetary value.
Also - I might add, that its literally comical, that US citizens are now going through an ultra nationalist phase. I mean, have you looked at your own "ancestry" polls recently?
http://www.businessinsider.com/largest-ethnic-groups-in-america-2013-8?IR=T
Your churches and believe systems still don't have to go away. Not in your lifetime, not in your sons lifetime. If you are coming from a believe system - that you are the only true and godloved group the truth is, that those never remained culturally "dominant" for all that long, new cultures always came and went, and if one remained the same for more than 200 years - you have anthropologists studying them as curiosities.
Also there is a thing called cultural assimilation - so over time, cultures mix - especially in the US - so you also will never be "on the outside", if you dont chose to be. If immigration politics are done right - and I can tell you, europeans have just taken in tens of millions of refugees from pridominantly islamic countries and our churches are still standing.
So is our conservative right.
They just grew stronger on a stance, that "the steady flow of immigrants - at some point has to stop" - which was more of a "instituitions were overwhelmed" issue, than anything else. (Economically motivated migrations are increasing as well, and apparently, also we are building walls and fences on other continents... But thats another unpleasant topic.)