First think about how most Christians "keep" Sunday
1. By far the majority of Christians DON'T keep Sunday, they may go to church on Sunday, but they are only "one hour" Sunday keepers, they do NOT keep the whole day.
I worked in a department store and since I take Saturdays off, I usually ended up working on Sunday. The interesting thing there was the fact we could always expect a large surge of customers around one o'clock every Sunday. Why? Well Sunday church was over, and people thought it was a good time to go shopping before they went home!

Also:
2. Most have been dismissing Saturday as God's special day, by saying -- "it doesn't matter WHAT day we devote to special time for worship. Any seventh day will do. Doesn't Paul say some esteem one day, others another day? Don't judge anyone about a day for Sabbath keeping, as Jesus is our Sabbath. Let's not be legalistic about keeping a day.

SO WHAT HAPPENS when a movement arises that says -- "We have to keep all day Sunday holy if we want to regain God's blessings in our land" and they start mandating Sunday keeping?

It's going to stimulate honest thinking people to seriously think about this whole matter.
The mandate is against what they thought the whole issue concerning a holy day was about.

There will be those thinking -- well, if the nation's trouble is caused by disregarding God's Sabbath, maybe it's important to keep the RIGHT Sabbath of God's commandments.

I think that God's people who are still in Babylon are beginning to awaken to the Sabbath/Sunday question.

On most of the forums, I am seeing non Adventist putting it forward and sharing it. Kind of jars one awake as shocking for some reason....

That is truly a sign of an awakening in the churches of spiritual Babylon.

Here is an example... https://christianforums.net/forums/sabbath_issues/
Much like the discussions in Christian Forums.. https://www.christianforums.com/forums/sabbath-and-the-law.1131/