For those with English as their main language, I would suggest that you start your genealogy research at:

1. FamilySearch.org and then the pages pertaining to Norwegian research. This is now the best place to look for help: glossaries, How-to-guides, maps, histories and links directly to church books from Norwegian parishes.  And, of course, the possibility of searching records. You will find loads of information there. And then when you have found them in the US and know everything there is to know about their life there, then it is time to go to the main site in Norway for records:
2. It is called Digital Archives. The link is to the English version. This site is a very large database containing many types of record. But most important are church books, as just about everybody in Norway was recorded in the parish register. There are also many helpful instructions and some background information about the various records. If you have no success in finding your Norwegian ancestor, try:
3. The Norwegian Historical Datasenter. This is the English version, not perfect, but easier than dealing with it in Norwegian. It is easier to search here, you do not have to use wildcards. You can write only the first letters of a name or a location. It is a work-around for misspellings or variations like Henrik (Henrich, Hendrik, Henry and so on.)
4. Now it might be time to find your ancestor in a book, newspaper or magazine and you should turn to the National Library. The library has a vision to digitize most records. 2,5 million newspapers have been digitized, almost everything that has been published. And a lot of other material is also scanned, the frontpage shows you what kind of material.
5. Do you want to find an item belonging to your family. Try a search in the 3,6 million items on DigitaltMuseum. Use the farm name or name of a person, and something might turn up. I found photos of brass knives that my great-great-grandfather had made around 1870.
6. If you need a detailed map, go to Norgeskart.no. Search a place name, find it in the right county. And scroll in and out to see what the terrain is like, what place names surround your family farm and get to know the area.
7. If you need to learn more about local history, go to Lokalhistoriewiki. The wiki contains 65,721 entries, and is edited by Norsk Lokalhistorisk Institutt, which is organized under the National Library of Norway. They edit the wiki, so the quality of entries is high. It has information about people, places, words or concepts and much more. And most photographers in Norway throughout history, where they worked and when. Here is the starting page for members of Landslaget for Lokalhistorie, that is all the historical societies in the different counties.
8. If more information and background is needed, use Store Norske Leksikon a printed encyclopedia that has now been published on the internet and is accessible for everybody. There are long articles about, for example, subjects in history, geography and medicine, all related to Norway.
9. The site Norway-Heritage is in English. It lists ships, shipping lines, sailing routes and much more, related to Norwegian emigration. You might find a picture of the ship that your ancestor sailed on.
10. And lastly, social media should be a go-to place for more information about our family. Use local Facebook groups from the area where your ancestor lived, invite your family to ones you start and see what pops up. I have found pictures that I did not know existed of my great-grandparents.

Remember that if you need to translate text, google can help you in more than one way.

Here is still another useful site; The Genealogy Society of Norway: https://slektogdata.no/nb/english/about-genealogy-society-norway