Hi. I know just how you feel about the need for a "Master tree". For many years, before I discovered Wikitree, I started using Reunion for Windows. I still have notebooks and shoeboxes full of scraps of paper and photos, but the only way I can see where I am up to is to look at my desktop program. Reunion is no longer available to run in a Windows environment, so a couple of years ago I tried Legacy. It took me a while to adjust and get used to a new program but I find it very good for my requirements.
Take note about the fact that computers can, do and will occasionally die suddenly and do backups religiously. And don't just do a back up to your computer's hard drive!!! Backups need to be done to an independent storage like the cloud, or an external drive or even to a friend's computer. Whatever, just do it.
And the best thing about Legacy is that they offer a free version. Yay. It doesn't have all the bells and whistles of the Deluxe version, but those features can be unlocked at any time, for a fee. The free version does everything I want. Give it a try. In fact, give as many free programs as you can find a try and then you'll be much better informed to make your own decision.
One more reason to have a "Master Tree" is to keep a record of those items that cannot be published on Wikitree. I have many photos and documents from the internet that I legally copy for my own private use that cannot be downloaded to Wikitree as that would be a breach of copyright.
Also, be aware that while you may initially consider that you are downloading your family history onto Wikitree, you don't "own" those profiles or that tree. Other genealogists, data doctors, and robots can and will add to and change what you have written. Some people take offence at this as they feel their work is somehow being downgraded. Of course, what is actually happening is that the quality of the information is being improved by the collaborative efforts of all involved.
And yes there are a lot of profiles from the US here. It doesn't matter. This is a world tree. Many/most/all? countries are represented (I have no idea how many). I am Australian and they even let us convicts enter data!