Hi JT, Canadian carriers are severely restricted when it comes to broadcasting into the United States as they don't own that spectrum. Signals from different carriers on the same piece of spectrum act as pure noise to each other, drowning each other out.
Due to the physics of RF, we can't have the signal dead stop right at the border so by necessity it is designed to fade close to the border in order not to interfere with the US carrier's signal. It works both ways, they need to fade so Gretna isn't flooded with interference. If you can pick it up further south, then we may need to be pull it back even more, unfortunately.
As Dan suggested, a directional booster pointing straight north would work. We could also look at installing a more customized solution in the future depending on what transport is available.
In the meantime I'll send a drivetest soon to obtain a better picture of what the situation is like there.