Siberia #11 Q to OP was the year of wobble by UK, It. The A is constant, 7/68-7/76 and inc FRG. Factions in US had a Mission to Kill MRCA. Key MRCA dates were: 17/7/68: Concept Phase MoU: FRG (2 Arms: LW, MFG), Canada (for the 4TAF AW role), UK (then only for 2TAF/UK-back-up AW role), Italy, Belg,Neths (AW role). During that Study, as it settled at 2 seats/deep intruder, 11/68 Belg left (unaffordable) and Canada left - PM Trudeau was then sceptical, not only of Canada or anybody's tactical AW, but of NATO itself (RCAF AW ceased 31/12/71).
14/5/69: Definition Phase MoU, FRG/It/UK, Neths Observer to 28/7/69, then out as unaffordable. Those defections were role-driven.
22/7/70: Development Phase MoU, FRG/UK, It from 9/70.
MDC F-15 had been selected by USAF in the superiority role 23/12/69; USAF Lightweight Fighter Prog then brewed, to 1972 fly-off contracts, YF-16, YF-17. DoD bombarded UK/FRG/It with any and every lure and threat, through Elections in all 3 Nations, to:
1/5/75: Long Lead Materials Release, Batch 1, 40 MRCA; 29/7/76: production Contract. Only then did they give up: in part because they had some success in their main aim, which was not to vassalise Euro-industry, but was to extract fair offset for the DM cost of young men lunching in Munchen. MRCA would be FRG's heaviest Defence Budget line item for a decade., so US needed its slice, and got it on TI GM/TFR, Litton INS and Main Computer.
MDC, GD, Northrop of course did want to vassalise Euro-Aero and in part succeeded with 348 Euro-assembled F-16s, and with defeating Panavia sales efforts, except (part of) RSaAF.
To OP's Q: Tornado lost no bid as AW deep penetrator, so the A to the cancellation whiff is: what would the Customer Arms have done:
* RAFG AW: F-4M/B61 would have continued until: Jaguar/WE177C as actual, to continue to later 1980s...then lapse as unaffordable;
* RAFG AD: MOTS F-15K, probably US-built, some UK content, but not engine (cost exceeds benefit);
* Luftwaffe IDS/ECR+MFG+ * ItAF AW: almighty political fracas, Mirages actual and not v.F-15G, and Euro F-16 for part of the roles;
* ItAF AD: F-15 modest local assembly, plus even more MDC civil structures contracts;
* RSaAF: more F-15s plus some Mirage 2000s.