It’s not quite as blameless as it sounds. It’s taken from Psalm 72, Verse 8: “He shall have dominion from sea to sea and from the river unto the ends of the earth.” Subtext: “So all you Indigenous peoples can just shut the heck up! Also, Quebec.”
“If we can send a legion to it, it’s our backyard” was, I believe, Rome’s motto
But you could use latifundium, perhaps: Non in latifundium meum, which in the UK might also be translated as “Geroff moi land!”
Exi e cohorte? Exi ex area?
Shakespeare: “To be or not to be”
Sinatra: “Doo-be Doo-be-doo”
It will be featured on the money, so
“This we’ll defend.”
This should be a poll.
E Pluribus Unum
“para bellum”
Resistance is futile
Soylent green is people
And we’re actually starting to say “From Sea to Sea to Sea” a fair bit these days (and maybe the last 10 years or so). Do any of my fellow Canucks know if the third “Sea” is official now?
Frank Sinatra: “One good take!”
I found these weird sunglasses and now all my money looks like this.
America … Fuck Yeah!
See also
But overall it’s probably the most appropriate motto of the whole thread, so worth mentioning twice. 
I don’t mind the old motto. But if updating:
- There’s a lady who’s sure all that glitters is gold
- Meet the new boss, same as the old boss
- You might be king of half the world, you’ll not own me as well
- He wore his gun outside his pants, for all the honest world to feel
- ain’t the kind of place to raise your kids, in fact it’s cold as hell
- I want to be the girl with the most cake
- And I said next time, Next time We’ll get it right
- Freedom’s just another word, for nothing left to lose
- Liberty, she pirouette, when I think that I am free
- I was flying back from Lubbock and saw Jesus on the plane
- Beautiful is the dream that makes you mine
- Have you come here to play Jesus, to the lepers in you head?
- Take a sad song and make it better
- We sick and tired of your ism-schism game
- Some folks inherit star-spangled eyes
- And found my cleanest dirty shirt
- Does anybody really know what time it is?
- Don’t go changing to try to please me
- Just a stranger on the bus, trying to make his way home
- Orangutans are skeptical of changes in their cages
- Smugglers, scramblers, burglars, gamblers
Pickpockets, peddlers and even panhandlers - so build me up, Buttercup
- Sippin’ on gin and juice (laid back), with my mind on my money and my money on my mind)
- I’m not big on social graces, think I’ll slip on down to the oasis
- And I loved you when our love was blessed, and I love you now there’s nothing left but sorrow and a sense of overtime
- You with the jaundiced eyes, drunk on your own reflection propped up with desks and flags
- was feeling as nearly faded as my jeans
- I said “do-you-speaka-ma-language?”
- And feeling good was good enough for me
- but if your hopes should pass away then simply pretend that you can build them again
- America when will you be angelic?
When will you take off your clothes?
Okay, so maybe these not-so-serious mottos don’t translate into Latin so well. But one point for every source you can name… 
He who dies with the most toys wins.
Pedit Semper Ridiculam (Farts Will Always Be Funny).
This says “He always farts the silly woman.” I think you want pedita semper ridicula.
Now write it a thousand times on the side of the White House.