I think you may be mis-understanding some knife terms. Your knife absolutely does have bevels if it is sharpened. In knife terminology, “bevel” doesn’t indicate the large visible slope that one might call a geometrical bevel; “bevel” indicates the surface that has been ground at an angle to the vertical plane of the blade. In the case of the Japanese single-beveled knife, the blade is thick, so you can see the gigantic bevel. In the case of a western style knife, the blade tapers to the edge from the spine, and the actual edge itself is sharpened on both sides, so if you hold a magnifying glass up to the edge, you’ll see that there are two bevels on it, though they are small. It is possible to make a thin, wedge-style blade where the inner face is truly vertical, so it would be single-beveled, but would not look like the Japanese style blade where the bevel is visible because the slope of the main surface goes all the way to the spine, and the actual fine edge grinding is small, but only on one side.
The fact that a western style blade is a wedge and is sharpened on both sides of that wedge makes it double-beveled. If you use such a knife to make thin slices, you will see the effect I was telling you about: instead of making thin vertical cuts, the bevel on the inside will push the blade out, and you will make wedges rather than truly vertical cuts.
For the sake of understanding the ergonomics and functional characteristics of the difference, may I recommend an experiment for you? Get a characteristic western knife or a double-beveled Japanese knife and a single beveled Japanese knife. (You should be able to obtain cheap single and double beveled knives at Daiso (they have them for $5-$8). Be sure to check the packaging for the little graphic indicating double or single bevel grinding. You can see from this one that this Santoku style knife is indicated as being double-beveled:
The ones that are single-beveled will have a little icon or picture indicating that they are single beveled.
Get a potato, a carrot, and a daikon, and try to slice potato chips and similarly sized slices from each of these. You will feel the difference, and then you can design your knife accordingly, knowing how the different bevels cut. What you will notice is that whereas the blades that are single beveled will slice potato chips off of a potato with even thickness, the double-beveled blades will not; the cut line will veer outwards and you will get wedges rather than slices.